Magnesium base alloy



' same tilne.

which manganese llnparts to magnesium al- Patented July 18, 1933 JOHN A. GANN, OF MIDLAND, MICHIGAN,

PANY, OF MIDLAND, MICHIGAN,

MAGNESIUM No Drawing. Application filed April 25,

The present invention relates to improved light weight alloys in which magnesium is the predominating constituent. One object of my invention is to produce magnesium base alloys possessing the characteristic low specific gravity approaching that of magnesium that at the same time possess a combination of useful properties such as to make these alloys valuable for use in the mechanical arts. Other objects and advantages will appear as the description proceeds.

Heretofore most of the commercial magnesium base alloys that possess high tensile strength contained aluminum as an essential alloying ingredient. combination with certain other alloying elements imparts valuable mechanical properties to magnesium base alloys, it has the dis advantage of decreasing the corrosion resistance when present in adequate amounts to impart high tensile strength. Moreover, this element very materially reduces the quantity of other elements, particularly maganese, which may be alloyed with magnesium at the Thus the valuable properties loys cannot be fully realized when aluminum is present as a principal alloying ingredient.

Many attempts have been made to produce high strength magnesium base alloys which do not contain aluminum and which at the same time are resistant to corrosion. Malleable alloys of this type are described in a copending application, Serial No. 593,193, filed February 15, 1932, which consist of a ternary combination of magnesium with cadmium and Zinc as alloying ingredients. I have now discovered that manganese can be alloyed more readily with the aforesaid magnesium-cadmium-zinc alloys than with those alloys containing aluminum, and useful alloys are thereby produced which are not only superior to the parent ternary and binary alloys, but also possess a tensile strength which is substantially as high as any previously known commercial magnesium base alloy, as well as a high degree of corrosion resistance.

Accordingly the alloys which are the subject of my invention contain the metals magnesium, cadmium, zinc, and manganese,

Although aluminum in PATENT OFFICE ASSIGNOR TO THE DOW CHEMICAL COM- wherein the magnesium content exceeds 75 per cent, the cadmium, zinc, and manganese are each present in amounts of over 0.1 per cent and the quantity of the three metals cadmium, zinc, and manganese together is less than 25 per cent of the total. I

Examples of my new improved quaternary alloys are given in the table showing their properties measured on extruded samples of the alloys, together with the properties of the parent binary alloys of magnesium and manganese, and those of the parent ternary alloys otmagnesium, cadmium, and zinc for comparison.

The data of the table indicates that the tenslle strength, yield point (defined as the load in lbs./sq. in. at which the stress-strain curve deviates 0.1 per cent elongation from the modulusiine) and hardness are improved in my new alloys compared to the previously known simpler parent alloys.

The herein described alloys may be cast, rolled, extruded or otherwise shaped by methods commonly used for magnesium base alloys and the proportions of the alloying ingredients are to be governed by the particular application in view. Compositions which are suitable for extrusion may contain from 0.1 to 15 per cent of cadmium, from 0.1 to 15 per cent of zinc, and from 0.1 to 2.5 per cent of manganese. As ageneral purpose light weight alloy, suitable compositions are from 0.1 to 10 per cent of cadmium, zinc 0.5 to 10 per cent, and 0.1 to 2 per cent of manganese,

Table Mechanical properties Alloy coml Tensile Yield Hardstrength point ness lbs./sq.in.lbs./sq'.in. Brinell 1. Binary alloy: M 99%, Mn 1% 36, 600 21, 800 39 2. Ternary alloy: d 2%, Zn 2%, balance Mg 32, 000 19, 200 41 3. Quaternary alloy: Ditto (2), plus 1% Mn 41, 200 32, 400 56 4. Ternary alloy: Cd 6%, Zn 2%, balonce Mg 37, 500 22, 500 44 15. Quaternary alloy: Ditto (4), plus 1 0 Mn 39, 400 27,600 47 8. emery alloy: Cd 4%, Zn 4%, balance Mg 37, 300 22, 200 41 7. Quaternary alloy: Ditto (6), plus the balance being magnesium. It is preferable, however, to employ from 0.5 to 1.5 per cent of manganese and from 2 to 8 percent of zinc and from 2 to 10 per cent of cadmium. Another example of alloys within the scope of this invention which are easily press forged consist of from 2 to 6 per cent of cadmium, 2 to 4 per cent of zinc, and 1 per cent of manganese, the balance being magnesium. The new quaternary alloys consisting of from 2 to 10 per cent of cadmium, from 0.1 to 3 per cent of zinc, and from 0.5 to 1.5 per cent of manganese, the balance being magnesium, are easily hammer forged in heated condition. For exceptionally high tensile strength the manganese content may be from 0.75 to 2 per cent, while that of cadmium may be from 6 to 10 per cent, and that of zinc from 2 to 10 per cent. For example, an alloy consisting of magnesium, cadmium, zinc, and manganese wherein the quantity of magnesium in the alloy is 85 per cent, that of cadmium, zinc, and manganese is 10, 4, and 1 per cent, respectively, has a tensile strength and yield point of 47,700 lbs/sq. in. and 35,000 lbs/sq. in., respectively, in the extruded condition.

These new alloys may be produced by melting the ingredients together under a suitable flux, in a. closed chamber or in an inert atmosphere, according to the usual methods of preparing magnesium alloys. The manganese may be also added to magnesium by allowing molten magnesium to react upon a reducible manganese compound and subsequently the other alloying ingredients may be added.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the proportions of the ingredients employed within the limits specified, rovided the ingredients stated by any 0 the following claims or the equivalent of such stated ingredients beemployed.

I therefore particularly point out and distinctly claim as my invention 1. As a new product, a magnesium alloy composed of the metals magnesium, cadmium, zinc, and manganese wherein the magnesium content is in excess of 75 per cent, that of cadmium and zinc each is from 0.1 per cent to 15 per cent, and that of manganese from 0.1 to 2.5 per cent.

2. As a new product, a magnesium alloy consisting of 0.1 to 10 per cent of cadmium, from 0.5 to 10 per cent of zinc, from 0.1 to 2 per cent of manganese, the balance being magnesium.

3. As a new product, a magnesium alloy consisting of from 2 to 10 per cent of cadmium, from 2 to 8.per cent of zinc, and from 0.1 to 2.5 per cent of manganese, the balance being magnesium.

4.. As a new product, a magnesium alloy consisting of from 2 to 6 per cent of cadmium, from 2 to 4 per cent of zinc, and approximately 1 per cent of manganese, the balance being magnesium.

5. As a new product, a magnesium alloy consisting of from 2 to 10 per cent of cadmium, from 0.1 to 3 per cent of zinc, and from 0.5 to 1.5 per cent of manganese, the balance being magnesium.

6. As a new product, a magnesium alloy consisting of 6 to 10 per cent of cadmium, from 2 to 10 per cent of zinc, from 0.7 5 to 2 per cent of manganese, the balance being magnesium.

JOHN A. GANN. 

